Method for glucose isomerization using xylose isomerase purified from Thermotoga Maritima and Thermotoga Neapolitana

Abstract

This invention is in the field of glucose isomerization enzymes. More specifically, the invention is directed to a novel xylose isomerase, a process for the preparation of this enzyme, the use of this enzyme in glucose isomerization processes, and glucose isomerization processes. The enzyme is preferrably derived from Thermotoga maritima or Thermotoga neapolitana. The enzyme has a temperature optimum above 90 DEG C., pH optimum in the range of from 6 to 7 and a residual activity at 90 DEG C. of more than 40% after 30 minutes and/or residual activity at 98 DEG C. of more than 20% after 30 minutes. The enzyme can also be in immobilized form.

We claim: 
     
       1. A glucose isomerization process, comprising reacting a feed liquor containing about 20 to 65% (w/w dry substance) glucose with a substantially purified xylose isomerase which is derived from Thermotoga maritima or Thermotoga neapolitana at a temperature of from 50° to 130° C., a pH of from 3.5 and 8 and a reaction time of from 10 seconds to about 5 hours, wherein the xylose isomerase has the following properties: (a) temperature optimum above 90° C.;   (b) pH optimum in the range of from 6 to 7; and   (c) a residual activity at 90° C. of more than 40% after 30 minutes and/or a residual activity at 98° C. of more than 20% after 30 minutes.   
     
     
       2. The glucose isomerization process according to claim 1, wherein the xylose isomerase has immunochemical properties identical or partially identical to those of the xylose isomerase derived from Thermotoga maritima DSM No. 3109 or Thermotoga neapolitana, DSM No. 4359. 
     
     
       3. The glucose isomerization process according to claim 2, wherein the xylose isomerase is derived from T. maritima DSM No. 3109 or a mutant thereof. 
     
     
       4. The glucose isomerization process according to claim 2, wherein the xylose isomerase is derived from T. neapolitana DSM No. 4359 or a mutant thereof. 
     
     
       5. The glucose isomerization process according to claim 1, wherein the xylose isomerase is in the form of an immobilized enzyme. 
     
     
       6. A glucose isomerization process, comprising (a) reacting a feed liquor containing about 20 to 65% (w/w dry substance) glucose with a substantially purified xylose isomerase which is derived from Thermotoga maritima or Thermotoga neapolitana at a temperature of from 50° to 80° C., a pH of from 6 and 8 and a reaction time of from 10 minutes to about 5 hours, to produce a high fructose syrup containing from about 40 to about 50% fructose; and   (b) reacting the high fructose syrup with the substantially purified xylose isomerase at a temperature of from 80° to 130° C., a pH of from 3.5 to 8 and a reaction time of from 10 seconds to about 5 hours to produce another high fructose syrup containing from about 50 to 60% fructose, wherein the xylose isomerase has the following properties:     (a) temperature optimum above 90° C.;   (b) pH optimum in the range of from 6 to 7; and   (c) a residual activity at 90° C. of more than 40% after 30 minutes and/or a residual activity at 98° C. of more than 20% after 30 minutes.   
     
     
       7. The glucose isomerization process according to claim 6, wherein the xylose isomerase has immunochemical properties identical or partially identical to those of the xylose isomerase derived from Thermotoga maritima DSM No. 3109, or Thermotoga neapolitana, DSM No. 4359. 
     
     
       8. The glucose isomerization process according to claim 7, wherein the xylose isomerase is derived from T. maritima DSM No. 3109 or a mutant thereof. 
     
     
       9. The glucose isomerization process according to claim 7, wherein the xylose isomerase is derived from T. neapolitana DSM No. 4359 or a mutant thereof. 
     
     
       10. The glucose isomerization process according to claim 6, wherein the xylose isomerase is in the form of an immobilized enzyme.